This invention is generally directed to liquid developer compositions and processes thereof and wherein there can be generated excellent developed images thereof in, for example, bipolar ion charging processes, and reverse charge imaging and printing development (RCP) processes, wherein a first charging device generates a positive or negative toner polarity, and a second charging device generates an opposite toner charge of a negative or positive polarity, reference U.S. Pat. No. 5,826,147, the disclosure of which is totally incorporated herein by reference, and wherein the developer contains no charge director, or wherein the developer contains substantially no charge director. Preferably the liquid developer of the present invention is clear in color and is comprised of a resin, a hydrocarbon carrier, and as a charge acceptor a polyethylene oxide-polypropylene oxide, Alohas, an aluminum-di-tertiary butyl salicylate, as illustrated in U.S. Pat. No. 5,563,015, the disclosure of which is totally incorporated herein by reference, including a mixture of Alohas and EMPHOS PS-900.TM., a cyclodextrin charge acceptance agent, or charge acceptance additive component, and an optional colorant.
The present invention is also specifically directed to a electrostatographic imaging process wherein an electrostatic latent image bearing member containing a layer of marking material, toner particles, or liquid developer as illustrated herein and containing a charge acceptance additive, which additive may be coated on the developer, is selectively charged in an imagewise manner to create a secondary latent image corresponding to the first electrostatic latent image on the imaging member. Imagewise charging can be accomplished by a wide beam charge source which generates free mobile charges or ions in the vicinity of the electrostatic latent image coated with the layer of marking material or toner particles. The latent image causes the free mobile charges or ions to flow in an imagewise ion stream corresponding to the latent image. These charges or ions, in turn, are accepted by the marking material or toner particles, leading to imagewise charging of the marking material or toner particles with the layer of marking material or toner particles itself becoming the latent image carrier. The latent image carrying toner layer is subsequently developed by selectively separating and transferring image areas of the toner layer to substrates like paper thereby enabling an output document.
The present invention also relates to an imaging process and imaging apparatus, wherein an electrostatic latent image including image and nonimage areas are formed in a layer of marking material, and further wherein the latent image can be developed by selectively separating portions of the latent image bearing layer of the marking material comprised of a liquid developer such that the image areas reside on a first surface and the nonimage areas reside on a second surface. In an embodiment, the present invention relates to an image development apparatus, comprising a system for generating a first electrostatic latent image on an imaging member, wherein the electrostatic latent image includes image and nonimage areas having distinguishable charge potentials, and a system or device for generating a second electrostatic latent image on a layer of marking materials situated adjacent the first electrostatic latent image on the imaging member, wherein the second electrostatic latent image includes image and nonimage areas having distinguishable charge potentials of a polarity opposite to the charge potentials of the charged image and nonimage areas in the first electrostatic latent image. The apparatus and process details can in embodiments be as illustrated in U.S. Pat. No. 5,826,147, the disclosure of which is totally incorporated herein by reference.
The liquid developers and processes of the present invention possess in embodiments thereof a number of advantages including the development and generation of images with improved image quality, the avoidance of a charge director, the use of the developers in a reverse charging development process, excellent image transfer, and the avoidance of complex chemical charging of the developer. Poor transfer can, for example, result in poor solid area coverage if insufficient toner is transferred to the final substrate and can also cause image defects such as smears and hollowed fine features. Conversely, over-charging the toner particles may result in low reflective optical density images or poor color richness or chroma since only a few very highly charged particles can discharge all the charge on the dielectric receptor causing too little toner to be deposited. To overcome or minimize such problems, the liquid toners, or developers and processes of the present invention were arrived at after extensive research. Other advantages are as illustrated herein and also include minimal or no image blooming, the generation of excellent solid area images, minimal or no developed image character defects, and the like.